Now Playing:Disaster looms- Disaster looms- The Explosion of Fukushima's Nuclear Reactor (Directly Filmed)
Description: Disaster looms in Japan Disaster looms in Japan New reactor failure heightens fears of a nuclear meltdown in quake-hit Japan.
COOLING systems failed at another nuclear reactor on Japan's devastated coast today, hours after an explosion at a nearby unit made leaking radiation, or even outright meltdown, the central threat to the country following a catastrophic earthquake and tsunami.
The Japanese government said radiation emanating from the Fukushima plant appeared to have decreased after yesterday's blast, which produced a cloud of white smoke that obscured the complex.
But the danger was grave enough that officials pumped seawater into the reactor to avoid disaster and moved 170,000 people from the area.
Japan's nuclear safety agency then reported an emergency at another reactor unit, the third in the complex to have its cooling systems malfunction. To try to release pressure from the overheating reactor, authorities released steam that likely contained small amounts of radiation, the government said.
Japan dealt with the nuclear threat as it struggled to determine the scope of the earthquake, the most powerful in its recorded history, and the tsunami that ravaged its northeast coast with breathtaking speed and power on Friday.
The official count of the dead was 686, but the government said the figure could far exceed 1,000.
Adding to the misery was a new, 6.2 magnitude earthquake - centred east of Tokyo - that today swayed buildings in the capital.
Meanwhile teams searched for the missing along hundreds of kilometres of the Japanese coast, and thousands of hungry survivors huddled in darkened emergency centers that were cut off from rescuers and aid.
The explosion at the nuclear plant, Fukushima Dai-ichi, 275km northeast of Tokyo, appeared to be a consequence of steps taken to prevent a meltdown after the quake and tsunami knocked out power to the plant, crippling the system used to cool fuel rods there.
The blast destroyed the building housing the reactor, but not the reactor itself, which is enveloped by stainless steel 15 centimetres thick.
Inside that superheated steel vessel, water being poured over the fuel rods to cool them formed hydrogen. When officials releas...